The air/tear interface is the most powerful focusing element of the eye. As we all know, corneal shape and regularity along with tear film health dictate tear film power, smoothness, and stability and together have a profound effect on image quality. The importance of a quality tear film is well known in vision and must be considered completely prior to performing any surgery on the focusing elements of the eye. John Doane, MD, Eric Donnenfeld, MD, and Douglas Koch, MD, do a wonderful job of bringing practical information to anterior segment surgeons on how to examine the tear film for both optical quality and physical health along with the tests and technologies that help them do so. How our refractive and cataract surgery measurements are affected by tear film abnormalities is also discussed. A great result in refractive and cataract surgery starts with a great tear film. Ideally it is optimized prior to surgery for optimal healing and vision. EyeWorld thanks these doctors for sharing their expertise on this powerful liquid focusing element that does way more than moisturize the ocular surface.

Vance Thompson, MD,
Refractive editor

Patients undergoing refractive cataract surgery have high expectations. To obtain the best outcomes for these patients, it is imperative to optimize the ocular surface prior to surgery. The first step in this process is tear film analysis.
“Tear film analysis in any form is critical,” said John Doane, MD, Leawood, Kansas. “A healthy tear film is essential for good vision. For patients undergoing surgery and even for patients trying to see with or without glasses, if you do not have a good tear film, game over.”
Eric Donnenfeld, MD, Garden City, New York, agreed and noted that he routinely uses point-of-service tear film analysis in evaluating all dry eye patients and the great majority of patients presenting for cataract or refractive surgery.

Types of tear film analysis

Dr. Doane said that he is a minimalist when it comes to tear film analysis. He uses topography and photokeratoscopy. “Photokeratoscopy specifically images the first Purkinje image, and that is the tear film. For me, that is a critical qualitative test. I immediately know if the tear film is good or not. Photokeratoscopy has always been wonderful, and if I’m ever worried about a patient, I will put him or her behind a manual keratometer, so I can assess how effective the tear film is in real time blink to blink and between blinks,” he said.
Dr. Donnenfeld uses tear osmolarity as the baseline testing that is performed on all patients. “I think it gives me the most information, but I do MMP-9 as well. Although it’s not a tear film analysis, I’ve started performing gland imaging on the great majority of my patients. I think performing LipiView [Johnson & Johnson Vision, Santa Ana, California] on my surgery patients is helpful in evaluating meibomian gland dysfunction,” he said.
Douglas Koch, MD, Houston, first looks at the mires from the Galilei (Ziemer, Port, Switzerland) measurement that he takes on every new and preop patient. “If the mires are good, that tells me that the tear film is good. The next thing I do is a basic slit lamp examination to look at the height of the tear film meniscus. If I have any questions, then I’ll get a tear breakup time. I have found that if I have a good tear breakup time with no staining, good tear meniscus, and good mires on the Galilei, I don’t need to go any further in terms of diagnosis or treatment,” he said.
If he observes abnormalities in the mires and he determines that the condition is not epithelial basement membrane dystrophy or Salzmann’s nodular dystrophy, and hence attributable to tear film issues, he will treat and continue to treat until he obtains good, clean measurements. “I also rely on the mires from the IOLMaster 700 [Carl Zeiss Meditec, Jena, Germany], which are the reflections from the LED lights, and the standard deviations of corneal measurements from the LENSTAR [Haag-Streit, Koniz, Switzerland] because those are good measures of the accuracy of my corneal readings,” Dr. Koch said.

Meibomian glands

Dr. Doane said he is a minimalist in evaluating the meibomian glands as well. “I do fluorescein and tear breakup time. I am more on the qualitative end than getting into the weeds with quantitative, which I think varies so much. I also get some benefit from Schirmer’s,” he said.
Dr. Doane added that he will assess meibomian gland secretions if he sees any sign of acne rosacea. “I think it’s important to get on top of that if you decide to do surgery,” he said.
Dr. Koch performs a slit lamp examination to observe the meibomian glands to see if they are obstructed. If there are abnormalities that might be associated with any form of blepharitis, he treats it preoperatively.

Before proceeding with surgery

If tear film abnormalities are observed, surgeons need to decide whether or not to proceed with surgery or to improve the tear film before continuing. “If the tear film is not normal on the front end, then we will have a discussion with the patient about optimizing the tear film before we proceed,” Dr. Doane said. “We would optimize it preoperatively, then proceed with surgery. However, there are situations postoperatively where you might do something from an iatrogenic standpoint and make things worse. For example, let’s say you do refractive cataract surgery, and you make any type of corneal incision or perform laser vision correction. Especially in older patients, these procedures may affect corneal sensation, which will affect the tear film. Surgeons have to be ready for that and manage any issues that arise.”
When treating a patient for dry eye, Dr. Donnenfeld uses tear osmolarity and MMP-9 to provide a baseline of the disease and to provide information as to the cause of the disease. “I then develop a treatment protocol based on my physical findings that correlate with the point-of-service testing. I use the point-of-service testing with osmolarity and MMP-9 to follow the patient’s response to therapy and to make sure he or she is responding in a good way. The point-of-service testing not only provides diagnostic information as far as the severity of dry eye, but it also provides me with good reproducible information about the patient’s response to therapy,” Dr. Donnenfeld said.
Dr. Donnenfeld commonly treats patients who have good vision with glasses and minimal or no corneal staining and minimal conjunctival staining. If a patient has physical findings of dry eye, such as lissamine green conjunctival staining or some corneal staining, he will treat him or her with aggressive therapy to resolve the problem. “I never perform surgery on a patient with active dry eye if I can avoid it. I want to manage the disease before I go on to surgery,” he said.

The future

According to Dr. Donnenfeld, MMP-9, which has been a qualitative test, will shortly become a quantitative test. Surgeons will get a numeric value of the amount of MMP-9. “That will give us a lot of important information. This will hopefully be available later this year. Then a variety of other point-of-service tests will become available. I think in the near future, we will have a litany of tests that will allow us to provide specific therapy to patients that will optimize their response to therapy based on testing,” he said.